ELECTRICAL-CONDUCTIVITY OF DISPERSIONS - A REVIEW

Measurement of the electrical conductivity of dispersions has been used in mineral processing systems, for example, to estimate level and gas holdup (in flotation cells) and as a substitute for pH measurement (e.g. in strongly alkaline slurries). The models of dispersion conductivity which are of potential interest in these systems are reviewed. Special attention is given to models which consider volume concentration, shape and size distribution of the dispersed phase, namely the models of Maxwell, Bruggeman and Fricke. The limitations of each model are addressed considering the basic assumptions in their derivation. It is shown that the shape of the dispersed phase affects the conductivity of dispersions if the aspect ratio is less than about 0.4; this effect is more pronounced when the dispersed phase is more conductive than the continuous phase. A critical conductivity ratio, CCR, is introduced which is the value of the ratio of conductivity of the dispersed and continuous phases above which the dispersion conductivity is insensitive to the dispersed phase conductivity. The practical implication of the CCR on the estimation of holdup and conductivity of the dispersed phase is discussed. Two equations to approximate the CCR for any given dispersion are proposed.